Disney does a poor job of explaining this ...
There are 2 separate services, Disney's Magical Express and Resort Airline Check-in. They aren't the same. They are totally separate.
Disney's Magical Express:
- available to everyone on every airline, as long as you're named on a WDW resort reservation
- round-trip motorcoach transportation between Orlando Int'l Airport and your WDW resort
- ONE-WAY automatic luggage transfer from the airport to your resort room
So just to make it clear, DME is for everyone. Even if you fly in on Fred's Airline and Crab Shack, you can still use DME to the fullest extent.
Resort Airline Check-in:
- available only to people flying on "participating airlines"
- think of it as curbside check-in for your FLIGHT HOME, only it's in your resort lobby rather than at the airport
- you check-in for your flight, get your boarding passes, and check your luggage through to your final destination
- has nothing to do with DME. Even people who don't ride DME can use RAC.
If you are getting a ride to the airport with DME and you aren't flying a "participating airline," you simply bring your luggage to the bus. The driver loads it under the bus, you get it right back after the bus parks, and you check-in with your airline like usual.
So to repeat one last time ... for your trip from home to WDW, airline doesn't matter -- EVERYONE gets the same DME treatment. On the trip from resort to the airport, some people can do curbside check-in at the resort and some can't ... this
is the only place where airline matters.